Pregnant women in Kenya have a similar risk of HIV infection during pregnancy as women in serodiscordant couples or sex workers, but women with a history of sexually transmitted infections (STIs) had nearly a 4-fold increased risk of acute HIV infection, John Kinuthia from the University of Nairobireported at the 21st Conference on Retroviruses and Opportunistic Infections (CROI 2014) last month in Boston.

In this prospective cohort study of pregnant and postpartum women in western Kenya, conducted between May 2011 and June 2013, more than half of all incident HIV infections diagnosed were acute infections detected during pregnancy or postpartum. The remaining incident infections were detected shortly after study recruitment and were estimated to have occurred prior to study entry.

These findings reinforce the need for repeat HIV testing during pregnancy and underscore the need to use more sensitive methods, including pooled nucleic acid amplification tests (NAAT), especially in regions with high HIV prevalence and incidence, Kinuthia noted. They also underscore the importance of screening for and treatment of STIs in HIV prevention.

While much remains to be done -- only an estimated 35% of pregnant women in low- and middle-income countries get an HIV test -- considerable progress has been made in the identification and treatment of women with HIV in prevention of mother-to-child transmission (PMTCT) programs.

The availability of effective antiretroviral therapy (ART) for prevention of perinatal HIV transmission and expansion of ART and access to PMTCT services in many countries in sub-Saharan Africa has resulted in significant declines in transmission rates. For example, Botswana and South Africa have reduced transmission rates to below 5%; without any intervention, transmission rates would range between 25% and 40%.

However, while women with chronic HIV infection are the primary target of PMTCT programs, the need to ensure that pregnant women without HIV do not acquire it is of no less importance. Women in the window period (before tests can detect infection) or those who acquire HIV after testing will often go unrecognized and untreated. Women with acute HIV infection have higher viral loads, putting them at increased risk of passing the virus on to their infants, especially if they are not taking antiretrovirals.

Within this context, the researchers chose to look at the rates and co-factors linked to acute HIV infection among pregnant and postpartum women.

Pregnant women testing HIV negative on 2 rapid HIV tests at their antenatal visit or within the previous 3 months were enrolled after consenting. They completed questionnaires on sexual behavior and socio-demographic characteristics. Blood was taken for nucleic acid testing and run in pools of 10 samples. Those who tested negative had tests every 1 to 3 months throughout the 9-month postpartum follow-up period. Genital swabs were collected for STI detection at baseline and throughout follow-up. Postnatal visits for the most part mirrored routine immunization visits.

Of the 4245 women seeking care at Ahero and Bondo district hospitals, where HIV prevalence at antenatal care clinics is 22% and 26%, respectively, 3408 were HIV negative and, of the 2351 eligible women, 1304 (56%) enrolled in the study.

These women had a median age of 22 years and 78% were married, for a median of 4 years. 7% reported a history of STIs. 1% of the women knew their partner was HIV positive while 34% did not know their partner’s status.

A total of 24 women had newly identified HIV infection, giving an overall HIV incidence rate of 2.34 per 100 person-years. Of these, 10 had a positive NAAT at enrollment (5 categorized as seroconversion and 5 as acute infection). 14 acquired HIV during follow-up: 2 late in pregnancy (week 32), 3 at 14 weeks postpartum, and 7 at 9 months postpartum.

Of the women with acute infection, none reported having an HIV positive partner. It is not uncommon for a man to test by proxy; if a woman tests negative at antenatal care, the partner assumes he is also negative, said Kinuthia. The partner’s status was not confirmed.

Women with a history of STIs had close to a 4-fold increased risk of acute HIV infection (odds ratio [OR] 3.8), while those who had syphilis or bacterial vaginosis at the time enrollment had 10-fold and close to 3-fold increased risk, respectively (OR 10 and 2.6).

Among women with and without HIV, maternal age, marital status, age difference from the partner, and infection with other STIs did not differ. Being married for a shorter period of time was associated with increased risk for acute HIV infection (OR 1.14).

Kinuthia stressed the need to prioritize strategies to detect and treat STIs. Other HIV prevention options should be aggressively promoted, he added, including PrEP, microbicides, and promotion of partner HIV testing and treatment.